Worldwide interest in renewable energy options has given rise to a rash of new wind turbine designs. Some of the most recent models on the market are vertical axis wind turbines (VAWTs) that are quiet, efficient, economical and perfect for residential energy production, especially in urban environments.
The prior art includes two vertical axis wind turbine (VAWT) designs. One form of the Savonius rotor can be visualized as a 55-gallon drum and cut it in half along a plane passing through the geometric axis of the drum which bisects the drum. Then the two halves of the drum are mounted on a shaft that rotates in a manner similar to an anemometer.
Another form is the Darrieus apparatus that resembles an egg beater. Essentially, it has two vertically oriented blades revolving around a vertical shaft. The blades are airfoils. These airfoils, like airplane wings, have a flat side and a curved side. The result of air passing over the two sides is a force known as lift. Because the airfoils are secured to a hub, which in turn is attached to a generator shaft the air passing over the airfoil shaped blades produces rotational movement which spins the generator.